Patent GB-161229-A (GB)
Title: Improvements in machines for grinding milling cutters and the like
IPC: B24B3/02
Filed: 1919-12-03
Abstract: 161,229. Marks, E. C. R., (Pratt & Whitney Co.). Dec. 3, 1919. Milling - cutters, sharpening; cutting-edges, shaping and treating.-In a machine for grinding the front radial, or approximately radial, faces of the teeth of milling-cutters, taps, reamers, and like tools, the grinding-wheel has a convex conical grinding-face adapted to have line contact with the straight or helicoidal cutting- faces of the cutter, which is adapted to be adjusted along lines parallel to the line of contact with the grinding-wheel; means for axially adjusting the wheel and for reciprocating and rotating the cutter, and for trueing the grinding-wheel, are also provided. The machine comprises a frame 6 on which is mounted in bearings 4, 5 a grinding- wheel 1 having a convex conical face 1<a>. The cutter is mounted on a holder 7 carried by a knee 8 movable on the frame, in a direction parallel to the line of contact of the grinding face with the cutter, by means of a screw 13. The cutter A, Fig. 6, is mounted on a mandrel B between a centre 17, adjustable on a table 19, and a centre 16 carried by an indexing-bead 18 mounted on the table. The table is slidable on a saddle 21 adjustably secured to a carriage 22 which is slidable on a turntable 25 pivoted on the knee 8 and secured in position thereon by bolts 27. The carriage 22 is moved by means of a rack 28 and a pinion and may be locked in adjusted position, and the table 19 is moved by a pinion 36 operated by a handle 38 and engaging a rack on the table; the stroke of the table may be limited by stops 40. When grinding helicoidal cutters, the turntable 25 is set to an angle corresponding with the inclination of the cutting-faces and the cutter is partially rotated, as it moves past the grinding-wheel, by a pinion 43 carried by the head 18 and engaging a rack 42 on the saddle 21. The pinion 43 drives, through gearing, a bevelwheel 52 which drives the spindle 53. In order to index the cutter to present another tooth to the grinding-wheel, the bevel-whe,el 52 is secured to a sleeve 61 rotatable on the spindle 53, and connected with the sleeve is a housing 62 enclosing an index-plate 63 secured to the spindle. This plate has notches in its periphery adapted to be engaged by a spring-pressed detent 64 carried by the housing; on withdrawal of the detent from a notch, the spindle may be turned by a handle 67. In order to apply feed to the cutter, the housing 62 is adjustable relatively to the sleeve 61 by means of a worm-wheel 68 carried by the sleeve and a worm 69 rotatable bv a knob 70. After adjustment, the parts may be locked by a bolt fitting a slot in the worm-wheel; a counterweight may be secured to the housing to take up lost motion. The grinding-wheel is dressed to give it the, required shape by a. dressing-tool 80, Figs. 1 and 2, carried by a slide 81 movable by means of a screw 83 along a guideway on a bracket 79 which is pivoted at 84, so that it may be moved to an inoperative position, on a slide 87 adjustable by a screw 88. In order to set the tool to move correctly to true-up the wheel, a gauge 89<a>, Fig. 12, having a front face 89b of the required form, is substituted for the grinding- wheei and is correctly positioned by a gauge element 89<d> which is supported on the centres 16, 17 and engages the face of the gauge. The dressing- tool is then set to move in contact with the face 89<b> of the gauge, after which the gauge is replaced by the grinding-wheel, which is set by means of the dressing-tool. The grinding-wheel is adjusted axially by movement of the slide 73 carrying the bearings 4, 5 by means of a screw operated by a hand-wheel 75; the amount of movement of the wheel is ascertained by an adjustable divided disc 98 and a zero mark 99. When grinding cutters with teeth having radial faces, the line of contact of a tooth with the grinding- wheel passes through, and meets the axis of the turntable on, the cutter axis; for cutters with non-radial faces, the grinding-wheel is moved axially the required amount by the hand-wheel 75. Water is supplied by a pump 90, and trays 93, 95, 97 and spouts are provided for collecting and circulating the water. For grinding the peripheral faces of the teeth of cutters, a cylindrical grinding-wheel is used.